Island



UNITED STATES PATENT OFFICE.

CRAWFORD M. FAIRBANKS, OF LINCOLN, RHODE ISLAND.

FILE.

SPECIFICATION forming part of Letters Patent No 371,184, dated October11, 1887.

(No modrl.)

To uZZ whom it may concern.-

Be it known that I, CRAWFORD M. FAIR- BANKS, of Lincoln, in the State ofRhode Island, have invented a new and Improved File; and I do herebydeclare that the follow iug specification is a full, clear, and exactdescription thereof.

File-blanks brought into shape by rolling 0r forging when hot haveremaining upon their surface a scale or coating of ferro oxide which itis necessary to remove before cutting the teeth. This scale or oXidehasheretofore been removed from file-blaul s by grinding; but such grindingnot only removes the scale or oxide, but more or less of the metal belowit. The percentage of metal thus unnecessarily removed will of coursevary somewhat acinvention. This I accomplish by submitting thefile-blank to the action of an acid solution before the cutting of theteeth thereon, which completelyremoves the oxide, but does not in anyway affect the exterior surface of the metal. This removal of the scalemay in some cases, particularly in making small files, be effectedbefore the bar has been reduced to its ultimate shape for cutting theteeth, the bar being rolled cold after the scale is removed.

I prefer sulphuric acid, although other acids may be used to make thesolution. The time required for the blanks to remain in the solutionwill of course depend upon its strength and temperature, and can bereadily ascertained by the workmen in charge.

\Vhat I claim as my invention, and desire to secure by Letters Patent,is

A file having its teeth out upon the metal surface exposed by theremoval by chemical agents of the scale or oxide from the surface of arolled or hammered blank.

CRAWVFORD M. FAIRBANKS.

W'itncsses:

WALTER B. VINCENT, M. O. HERsEY.

